This invention relates to a magnetic refrigerator using a working material which radiates heat when it is magnetized and absorbs heat when it is demagnetized.
Magnetic refrigerators are based on the well-known phenomenon that working materials consisting of rare-earth-metal compounds, such as gadolinium-gallium-garnet (Gd.sub.3 Ga.sub.5 O.sub.12, abbreviated GGG), or alloys, such as an alloy of erbium and nickel, radiate heat when they are magnetized and absorb heat when they are damagnetized. The temperature of the working material is lowered by adiabatic demagnetization. The working material lowered in temperature extracts heat from an object to cool it. These magnetic refrigerators have an advantage over conventional gas refrigerators in having improved refrigerating capacity per unit volume of the object for cooling.
The magnetic refrigerators require two heat exchanging processes to be executed alternately; a heat discharging process for discharging heat generated from a magnetic material or working material by adiabatic magnetization, and a heat absorption process for extracting heat from the object by means of the working material cooled by adiabatic demagnetization. To obtain a high-efficiency refrigerating cycle through the two alternating heat exchanging processes, it is necessary to securely prevent heat transfer from the working material to the object in the heat discharging process, and to quickly transfer heat from the object to the working material in the heat absorption process.
A prior art magnetic refrigerator is provided with chambers for individually executing the heat discharging and absorption processes so that the working material alternately enters the chambers. For efficient heat exchange, it is necessary to fully maintain the air-tightness between the working material and chambers. In practice, however, it is technically difficult to securely seal the working material and the chambers. Insufficient sealing leads to a reduction in refrigerating efficiency. Moreover, the need of a transfer mechanism for the working material complicates the construction of the refrigerator.